Tsitsipas broke the 27-year-old three times and held off a late comeback from the Argentine to move into the quarter-finals. The World No. 15 broke through in 2018, reaching finals at the Barcelona Open Banc Sabadell and the Rogers Cup and winning titles at the Intrum Stockholm Open and in Milan. Tsitsipas will next face Italy's Andreas Seppi, who beat Slovakian Martin Klizan 7-6(2), 6-2.

Watch: Tsitsipas Serves Up Sushi Doughnuts, Sydney Fish Market

Third seed Diego Schwartzman also gained his first win of the new season, breaking Spain's Guillermo Garcia-Lopez five times en route to a 6-2, 6-3 win. The Argentine will face Yoshihito Noshioka for a spot in the semi-finals. The Japanese left-hander routed Russian Andrey Rublev 6-3, 6-1.

Brisbane native John Millman beat seventh seed Marton Fucsovics 6-3, 6-4 to advance to the quarter-finals in Sydney for the first time. The 29-year-old converted three of four break points throughout the 78-minute contest and will meet fourth seed Gilles Simon for a semi-final spot. The 2011 champion (d. Troicki) withstood 22 aces en route to a 7-6(5), 6-7(6), 6-4 win over Sam Querrey.